Typhus is any of several similar diseases caused by Rickettsia bacteria, seems to spread by lice, fleas, ticks, or rodents. The name comes from the Greek typhos (τῦφος) meaning smoky or hazy, describing the state of mind of those affected with typhus. The causative organism Rickettsia is an obligate parasite bacterium that cannot survive for long outside living cells. Typhus should not be confused with typhoid fever. While “typhoid” means “typhus-like”, the diseases are distinct and are caused by different species of bacteria.